1. Field of the Invention
The present invention concerns an electromyograph wherein the data detected on the patient is transmitted to the receiving unit without the use of metallic conductors, for instance by optical means or by radio communication.
The electromyograph is a medical instrument used to detect the electric muscular activity by means of surface electrodes applied on the patient's skin, or by means of needle electrodes inserted into the patient's muscle in the body parts of which the muscular functionality needs to be studied. The instrument is used more and more frequently to study the physiology of the muscular apparatus in healthy subjects and to thus acquire data for use in the study and treatment of muscular pathologies and, in particular, in therapies to recover the muscular functionality of previously injured parts.
2. Description of the Prior Art
The electromyograph of known technique uses the same technology of the already known and tested instruments for detecting the electric activity of other organs of the human body, as for instance the electroencephalograph or the electrocardiograph, and it hence consists of a table instrument from which a plurality of electric cables are connected to electrodes suitably fixed to the patient's body. This technique, which has given and still gives satisfactory results in the study of the heart and brain functions, has instead not given equally satisfactory results in the study of the muscular functions. This technique depends on a variety of factors, all however substantially leading to the fact that the muscular functions have to be measured while the muscle is contracting and thus in a dynamic condition, as opposed to the previously cited functions which can be taken in a fully static condition.
This objective requirement involves in fact some serious drawbacks which have prevented up to date the hoped for wider spreading of electromyographs, and the studies and cognitions connected thereto.
Among these drawbacks, one should remember in the first palce the need to dispose of sufficiently long electric cables, allowing them to follow the patient's movements which are at times particularly outstretched as, for example, in the case of deambulation; the problem is not, in fact, to simply dispose of cables of the required length, but rather to allow the patient to perform sufficiently free and natural movements in spite of the presence of such cables. The actual cable must therefore be kept rolled up on a bobbin and must be unrolled on pulleys up to the point of reaching the patient, whereby it is easily subject to mechanical failures at the points of higher stress.
A second serious problem concerns the patient's protection against electric shocks; the patient is in fact physically connected to the power mains through the electromyograph and the cables connecting the electrodes, i.e. through metallic conductors, insulation being guaranteed only by the presence of suitable electronic insulating devices allowing to transmit the electric signals but not the electric current, for instance by interrupting the metallic conductors through electric optical devices. Such insulating devices may however be subject to failures or damage, whereby there is always the danger of current leakages between the main circuit and the electric circuit detecting the signal and contacting the patient. The laws providing for safety measures on such instruments are hence becoming stricter and stricter, thereby involving high construction costs, especially when the instruments have also to be used --as in the present case--in dynamic conditions, which objectively increase the possibilities of accidental damages.
A third drawback is tied to the fact that the electric activity at muscular level is very feeble and thus must to be considerably amplified so as to be perceived by the instruments. The electric interferences which may overlap the signals coming from the muscular activity, and consequently modify them, are therefore particularly troublesome; these no doubt include the interferences generated by the movement of the electric cables connecting the electrodes to the instrument within the electromagnetic fields existing in the environment, and those deriving from the impedance variations of the electrode/patient interface.
The object of the present invention is to thus supply an electromyograph apt to overcome all the above mentioned drawbacks, allowing the patient to be constantly and perfectly insulated from the main electric circuit, allowing him a wide freedom of movement, and finally eliminating the electric interferences determined by the movement of the metallic cables transmitting the electric signals.